Your Question

Is there any genetic link between trisomy 13, dextrocardia with situs inversus, and Hirschsprung's disease? I have had children affected with each of these conditions. What are the chances of having more children affected with these conditions in the future?

Our Answer

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Has a genetic link been established between trisomy 13, dextrocardia with sinus inversus, and Hirschsprung's disease?

An extensive search of available literature does not currently yield the presence of any genetic-based connection between any of these three disorders. They are not known to typically occur together in one individual or in families, nor are they known to be caused by similar abnormal genetic or developmental processes.

Last updated: 2/2/2011

What causes trisomy 13?

Most cases of trisomy 13 are not inherited and are caused by random events during the formation of eggs and sperm in healthy parents (prior to conception). The condition typically results from having three copies of chromosome 13 in each cell in the body, instead of the usual two copies. This is referred to as complete, or full, trisomy 13. The extra genetic material disrupts the normal course of development, causing the characteristic features of trisomy 13.

Trisomy 13 can also occur when part of chromosome 13 becomes attached (translocated) to another chromosome during the formation of reproductive cells (eggs and sperm) or very early in fetal development. This is referred to as translocation trisomy 13. Individuals with this type have two normal copies of chromosome 13, plus an extra copy of chromosome 13 attached to another chromosome.

In rare cases, only part of chromosome 13 is present in three copies in each cell; this is called partial trisomy 13. In other rare cases, a person has an extra copy of chromosome 13 in only some of the body's cells; this is called mosaic trisomy 13. The severity of mosaic trisomy 13 depends on the type and number of cells that have the extra chromosome.[1]

Last updated: 1/20/2015

Is trisomy 13 inherited?

Most cases of trisomy 13 are not inherited and result from random events during the formation of eggs and sperm in healthy parents. An error in cell division called nondisjunction results in an egg or sperm cell with an abnormal number of chromosomes. For example, an egg or sperm cell may gain an extra copy of chromosome 13. If one of these contributes to the genetic makeup of a child, the child will have an extra chromosome 13 in each cell of the body.[1] For a woman who has never had a pregnancy or child with a trisomy, the risk to have a pregnancy with a chromosome abnormality would typically be her age-related risk; the risk increases with maternal age. For a woman who has had an affected pregnancy or child in the past, the risk is generally quoted as about 1% or the maternal age-related risk - whichever is higher at the time of pregnancy.

On the other hand, translocation trisomy 13 can be inherited. An unaffected person can carry a rearrangement of genetic material between chromosome 13 and another chromosome. These rearrangements are called balanced translocations because there is no extra or missing material from chromosome 13. A person with a balanced translocation involving chromosome 13 has an increased chance of passing extra material from chromosome 13 to their children.[1] Individuals interested in learning about their personal risk to have a child with a chromosome abnormality should speak with their health care provider or a genetics professional.

Last updated: 1/20/2015

What causes dextrocardia with situs inversus?

The exact cause of dextrocardia with situs inversus is not known, but the condition results from the abnormal positioning of the internal organs during fetal development. More than 40 genes have been identified as being required for the positioning and patterning of the organs in the body. Mutations in 9 different genes have been reported in individuals with either heterotaxy syndrome (when only some organs are involved) or situs inversus totalis, which suggests that in at least some individuals with either of these conditions, the cause may be genetic.[2] However, because a specific genetic cause has not been identified (and inheritance patterns have not been confirmed), it is difficult to estimate recurrence risks for the condition. Individuals interested in learning about their personal risk to have a child with this condition should speak with their health care provider or a genetics professional.

Some individuals with dextrocardia with situs inversus have it as part of an underlying disorder called primary ciliary dyskinesia, which is characterized by chronic respiratory tract infections, abnormally positioned internal organs (situs inversus), and the inability to have children (infertility). Primary ciliary dyskinesia is known to result from mutations in several different genes, but in many people with primary ciliary dyskinesia, the cause of the disorder is unknown. This condition is typically inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.[3] When 2 individuals who are carriers for an autosomal recessive condition have a child, there is a 25% (1 in 4) chance for the child to have the condition, a 50% (1 in 2) chance for the child to be a carrier like each of the parents, and a 25% chance for the child to not have the condition and not be a carrier.

Last updated: 4/23/2012

Is Hirschsprung's disease inherited?

Hirschsprung's disease (HSCR) usually occurs occurs by itself without other symptoms and is called isolated HSCR. Isolated HSCR has multifactorial inheritance, which means that multiple genes interact with environmental factors to cause the condition. When someone has a child with isolated HSCR, the overall risk to have another child with the condition is 4%. There are some factors that can change the risk. For example, the risk is higher if the sibling has long-segment disease rather than short-segment disease. Also males are more likely than females to develop HSCR. Another factor is if the siblings have the same or different parents.[4]

Individuals who are interested in learning about their personal risks or risks to family members should speak with their health care provider or a genetics professional.

Last updated: 9/19/2014

How can I find a genetics professional in my area?

Genetics clinics are a source of information for individuals and families regarding genetic conditions, treatment, inheritance, and genetic risks to other family members. More information about genetic consultations is available from Genetics Home Reference. To find a genetics clinic, we recommend that you contact your primary healthcare provider for a referral.

The following online resources can help you find a genetics professional in your community:

The American Society of Human Genetics maintains a database of its members, which includes individuals who live outside of the United States. Visit the link to obtain a list of the geneticists in your country, some of whom may be researchers that do not provide medical care.